Chromosome 3 is a large metacentric chromosome encompassing 7% of the human genome, about 210 megabases. The long range goal of this project is to construct a physical map of chromosome 3 and to isolate overlapping clones for the entire chromosome. First, a battery of useful markers will be isolated consisting of highly polymorphic VNTR (variable number of tandem repeat) probes and potentially transcribed regions of chromosome 3. These markers will be mapped to broad regions of chromosome 3 using a panel of somatic cell hybrids. A panel of radiation hybrids will be examined to produce a refined map of the chromosome. Radiation hybrids clones will bridge the gap between conventional somatic cell mapping and the level of resolution obtained by recombinant DNA clones and pulsed field gel electrophoresis. The radiation hybrid clones will also be the source of nested cosmid and YAC (yeast artificial chromosome) clones for a given region of the chromosome. A rudimentary linkage map of the most polymorphic markers will be used to compare the distances on the physical and linkage maps of chromosome 3.